1. Field of the Invention
The present invention relates to lasers and particularly to a laser diode pumped 2.8 micron solid state laser with high slope efficiency at or near room temperature.
2. Description of the Prior Art
It is well known that the human body is comprised of approximately 70% water, with various human tissues containing about 60% to 90% of water, and bone and cartilage containing about 30% to 40% of water. Since the 2.8 micron wavelength has a substantially maximum absorption in water, this 2.8 micron wavelength is the ideal wavelength to use for a large variety of medical laser applications on the human body. The 2.8 micron wavelength also offers a controlled absorption or penetration depth of, for example, one micron in the human body. As a result, this 2.8 micron wavelength is extremely useful in surgical applications where very precise cuts in area and/or depth are needed while minimizing damage to good tissue, bone and/or cartilage adjacent to, or under, the area to be ablated. A 2.8 micron wavelength laser could be used for precise surgery in such exemplary applications as brain surgery, neurosurgery, eye surgery, plastic surgery, burn treatment and the removal of malignancies.
Current lasers for generating this 2.8 micron wavelength use a variety of host or lasant materials with various pumping techniques for exciting the lasant material. Typically these lasers are flash lamp pumped. Such flash lamp pumped lasers are large, inefficient and expensive.
The present inventors attempted to develop a miniaturized 2.8 micron laser using a diode-pumped, 8% erbium-doped YLiF.sub.4 crystal laser. Such a laser barely produced a continuous wave (CW) output and only had a slope efficiency of 0.7%. This previous laser is described in an article entitled "CW and Pulsed 2.8 .mu.m Laser Emission from Diode-Pumped Er.sup.3+ :LiYF.sub.4 at Room Temperature" by G. J. Kintz, R. Allen, and L. Esterowitz, published in Appl. Phys. Letts., Vol. 50 (22), pp. 1553-1555 (June 1, 1987).